Brake lights go out cannot shift out of park

EAB13757

MEMBER
1994 FORD MUSTANG
5.0L
V8
AUTOMATIC
180,000 MILES

I have the car listed above GT model. Sometimes the brake lights go out and when that happens I cannot shift out of park or I have to press the button on the shifter real hard. Why is this happening and why is it only sometimes? What do I do to fix it?

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning.

It could be the brake light switch. That switch also controls the interlock solenoid. It is not working, it will not allow shifting out of park.

Check the switch under the dash. It is right at the brake pedal and has an electrical connector. Make sure it is tight and clean and that the switch is free to move.

Roy

NOTE: Perform this test only when brake application will not disconnect speed control system.

1. Check stop lamp operation by applying approximately 6 lb of pressure to brake pedal. If more than 6 lb of pressure is required, check brake pedal actuation and stop lamp switch.
2. If stop lamps do not function properly, check stop lamp switch, circuit fuse or bulbs.
3. If stop lamps function properly, check for battery voltage on circuit 296 at amplifier six pin connector.
4. Depress brake pedal until stop lamps are lit.
5. Check voltage on light green lead (circuit 511) at amplifier 6 pin connector. Difference between this and voltage reading in step 3, must not exceed 1.5 volts.
6. If voltage difference is greater than 1.5 volts, a high resistance in circuit exists which must be found and corrected.
7. Perform Vacuum Dump Valve Test. See: Cruise Control > Component Tests and General Diagnostics > Vacuum Dump Valve Test

replacement procedure

1. Disconnect wires at connector.

Fig. 3 Stop light switch replacement
imageOpen In New TabZoom/Print

2. Remove hairpin retainer, then slide switch, pushrod and nylon washers and bushing away from pedal and remove switch.
3. Position switch so U-shaped side is nearest brake pedal and directly over/under pin.
4. Slide switch up/down, trapping master cylinder push rod and blade bushing between switch side plates.
5. Push switch and push rod assembly firmly toward brake pedal arm, then assemble outside white plastic washer to pin and install hairpin retainer to trap whole assembly.
6. Assemble wire harness connector to switch and install wires in retaining clip.

NOTE: Switch wire harness must have sufficient length to travel with switch during full stroke of brake pedal. If wire length is insufficient, reroute harness or service as required.

7. Check switch for proper operation.

Image (Click to make bigger)